Rapid Ca2+-mediated activation of Rap1 in human platelets - PubMed (original) (raw)

Rapid Ca2+-mediated activation of Rap1 in human platelets

B Franke et al. EMBO J. 1997.

Abstract

Rap1 is a small, Ras-like GTPase whose function and regulation are still largely unknown. We have developed a novel assay to monitor the active, GTP-bound form of Rap1 based on the differential affinity of Rap1GTP and Rap1GDP for the Rap binding domain of RalGDS (RBD). Stimulation of blood platelets with alpha-thrombin or other platelet activators caused a rapid and strong induction of Rap1 that associated with RBD in vitro. Binding to RBD increased from undetectable levels in resting platelets to >50% of total Rap1 within 30 s after stimulation. An increase in the intracellular Ca2+ concentration is both necessary and sufficient for Rap1 activation since it was induced by agents that increase intracellular Ca2+ and inhibited by a Ca2+-chelating agent. Neither inhibition of translocation of Rap1 to the cytoskeleton nor inhibition of platelet aggregation affected thrombin-induced activation of Rap1. In contrast, prostaglandin I2 (PGI2), a strong negative regulator of platelet function, inhibited agonist-induced as well as Ca2+-induced activation of Rap1. From our results, we conclude that Rap1 activation in platelets is an important common event in early agonist-induced signalling, and that this activation is mediated by an increased intracellular Ca2+ concentration.

PubMed Disclaimer

Similar articles

Cited by

References

    1. Science. 1993 Nov 12;262(5136):1065-9 - PubMed
    1. Biochem J. 1995 Aug 15;310 ( Pt 1):263-9 - PubMed
    1. EMBO J. 1993 Sep;12(9):3475-85 - PubMed
    1. Thromb Haemost. 1993 Dec 20;70(6):884-93 - PubMed
    1. J Biol Chem. 1994 Jun 24;269(25):17257-61 - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources